In the past few decades, the demands made by physicians and patients on the functionality of implants have steadily increased. In this connection the rising human life expectancy plays a decisive part since it increases the need for biocompatible medical implants. For this reason, a new generation of implants is required which have the capability of growing into the bone faster and achieving a better connection with the bone. Furthermore, modern implants of such type are required to be mechanically stable and combine with the body's own tissue in an optimum fashion within a minimum of time, accompanied by the requirement of preventing a rejection reaction or even an infection.
It is known here that an optimized adaptation in particular of the implant surface to the complex biological environment is particularly important. This adaptation is in many cases achieved by a modification of the implant surfaces, for example by a coating that allows the surface properties to be designed irrespectively of the properties of the material of the implant. Especially the surface properties of the implants are of a special significance since cell and bacterial adhesion processes are known to be highly dependent on the surface quality of the implant. In this connection, above all the chemical composition and the roughness of the surface play a significant role.
A large number of the implants currently produced are made of titanium or a titanium alloy since titanium has long stood the test as a biocompatible material. Titanium has a high mechanical strength and, furthermore, distinguishes itself by its excellent biocompatibility. A disadvantage of this material, however, is that it takes a long time until a firm connection is obtained between the bone and the implant, that is, until the implant has grown in.
It is further known that the surfaces are modified in implants that are used for orthopedic purposes, so that an optimum integration of the orthopedic implants can be attained.
Implants of the type discussed above have a metallic surface so that, for aesthetic reasons, they do not provide an optimum solution for the dental field since their coloring is distinctly different from the natural colors of the tooth or of the gums. In the event of a peri-implantitis, the implant neck may become exposed as a consequence of the receding gums, so that the dark metallic implant material will show through at that point, which is inacceptable from a cosmetic point of view.
For this reason, in the dental field implants are increasingly used which are built up of a ceramic substrate as a base body. These ceramic implant materials likewise have a high strength as well as biocompatibility. However, compared to an implant made from a titanium material, the integration of the implant into the bone is more difficult. This is primarily due to the absence of osteoconductive properties, which would facilitate the ongrowth of osteoblasts on the surface. The cell adhesion processes are therefore impaired, and a loosening of the inserted implant occurs due to an insufficient bony connection of the implant surface with the bone. This inadequate adhesion can at best be marginally improved by an additional incorporation of bone cement. Moreover, in comparison with titanium materials, the adhesion of bone cements on ceramic materials is also noticeably reduced.
A number of approaches to functionalizing an implant manufactured from a ceramic material are known from the prior art, none of which, however, provides a satisfactory result. For one thing, efforts are made to apply titanium or titanium alloys on ceramic materials to combine the advantages of both materials with each other in this way. Among other things, this is made difficult because the two materials only produce a mechanical connection, with no chemical connection being developed between the two materials. For this reason, it is necessary to first roughen the ceramic surface in order to produce as good a mechanical connection as possible between the ceramic implant and the titanium coating or titanium alloy coating.
In addition, WO 2009/036845 A1 discloses a method of applying a titanium alloy onto a ceramic substrate. The titanium alloy is applied onto the ceramic substrate by means of plasma spraying here, so that at least satisfactory adhesive tensile strengths are achieved. But the ceramic implant needed for this has an appropriate roughness which allows the adhesion of the titanium sprayed on. Therefore, in this known method a pretreatment of the ceramic material is necessary in order to ensure the required adhesive tensile strength.
The object of the present invention is to provide an improved method for the manufacture of a functionalized implant, which allows a rapid, force-fitting biologization of an implant surface.